A road-rage murder trial has been aborted after two days when a juror realised they knew information about the case which meant they should not be serving.

Shayd Robinson, 20, is charged with murdering father-of-two Aaron Hadfield following a confrontation in the Lower Hutt suburb of Stokes Valley in January.

On Wednesday in the High Court at Wellington Justice Ron Young dismissed the jury after one of them realised they should not have been there because they knew information about the case, Fairfax reports.

The jury was already down to 11 people after another juror left on Monday.

Earlier, witnesses said they saw a frenzy of punching from two men through the driver's window of Mr Hadfield's car, Robinson licking a small knife and then saying "I like the taste of your blood".